(a) Field
The present invention generally relates to a method and an apparatus for managing a carrier of a multicast and broadcast service (MBS).
(b) Description of the Related Art
The MBS is a point-to-multipoint transmission scheme for concurrent transport of data packets from a source to a plurality of destinations. A broadcast service is a service where data packets are transmitted to all users, and a multicast service is a service where data packets are transmitted to users belonging to a specific group.
In a wireless access system supporting multi-carrier (hereinafter referred to as “a multi-carrier system”), two types of carriers exist in a position of a terminal. One is a primary carrier for transmitting traffic and a control signal between a base station and the terminal. The other is a secondary carrier that is an additional carrier for the primary carrier. The secondary carrier is used to transmit the traffic, or a special instruction or rule notified through the primary carrier is applied to the secondary carrier.
The terminal may switch a physical layer connection from the primary carrier to the secondary carrier by instruction of the base station. This is called carrier switching. The terminal returns to the primary carrier after being connected to the secondary carrier for a predetermined time, and does not communicate with the base station through the primary carrier while staying on the secondary carrier.
In an MBS service, the terminal may receive MBS-associated data through an MBS carrier corresponding to the secondary carrier. In this case, MBS configuration information is transmitted from the terminal to the base station through an MBS configuration (MBS-CFG) message. The terminal receives the MBS configuration information and an MBS MAP, and acquires a time when content of the joined MBS is transmitted through the MBS MAP. The base station may clearly notify the terminal of a transmission time of the MBS configuration, or the terminal may blindly recognize the transmission times. That is, when the terminal joins the MBS to initially receive the service, the base station notifies the terminal of the transmission time of the MBS-CFG message or transmits the MBS-CFG message at the predetermined time. The terminal can analogize or recognize the transmission time of the MBS MAP through the MBS-CFG message or recognize the transmission time of the content through the MBS MAP.
As such, the terminal can recognize the time for receiving the MBS-associated data, thereby recognizing a time for switching to the MBS carrier. However, when the terminal simultaneously receives the MBS service and a general service, the terminal cannot recognize a time for returning to the primary carrier for receiving the general service.